Surface properties of polymers are commonly modified by exposure to low-temperature oxygen or air plasmas for a variety of applications.  It is generally assumed that plasma treatment only affects the surface, with surface-specificity often cited as an advantage of the process. We used vibrationally-resonant sum-frequency generation spectroscopy to study the effects of plasma treatment on the orientation of phenyl rings in polystyrene thin films.  Plasma treatment of films on conducting substrates introduces anisotropy in the bulk by partial alignment of phenyl rings.  This alignment occurs even when the free surface is not directly exposed to the plasma.  Plasma treatment of polystyrene films on dielectric substrates chemically modifies the free surface without measurably altering bulk orientation.  This study shows that plasma treatment can induce bulk modifications that are substrate-dependent.

Effects of low-temperature plasma treatment on the surface and bulk orientation of polystyrene

244th National Meeting (2012)

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